ELECTROPHORETIC LIGHT-SCATTERING OF ALKYLDIMETHYLAMINE AND OLEYLDIMETHYLAMINE OXIDE MICELLES

Electrophoretic light scattering measurements were performed for aqueo us NaCl solutions of dodecyl-, tetradecyl-, and oleyldimethylamine oxi des (C12DAO, C14DAO, and ODAO). Electrophoretic mobility for 0.1 M NaC l solutions of C14DAO changed from negative to positive, as degree of protonation was increased. NaCl solutions (0.03 M) of ODAO displayed s imilar behavior, and their positive mobility increased with degree of protonation. On the other hand, 0.05 M NaCl solutions Of C14DAO presen ted three kinds of electrophoretic mobility at approximately -2.5 x 10 (-4), approximately 0, and approximately 2 x 10(-4) cm2 V-1 s-1 depend ing on degree of protonation, and there were transitions from negative to zero and from zero to positive at narrow degrees of protonation. A similar result was also obtained for 0.05 M NaCl solutions Of C12DAO. The electrophoretic mobility is related to the electrostatic potentia l of a micelle which is affected by degree of protonation of a micelle and counterion binding. Experimental results are qualitatively explai ned in relation to the variation of such parameters.